Śatapatha Brāhmaṇa ("of a hundred paths") 8.1.3.6

8.1.3.6

tadyāḥ purastādupadadhāti | tāḥ prāṇabhṛto 'tha yāḥ paścāttāścakṣurbhṛtastā apānabhṛto 'tha yā dakṣiṇatastā manobhṛtastā u vyānabhṛto 'tha yā uttaratastāḥ śrotrabhṛtastā udānabhṛto 'tha yā madhye tā vāgbhṛtastā u samānabhṛtaḥ

Those (bricks) which he lays down in front are the holders of the upward air (the breath, prâna); those behind are the eye-holders, the holders of the downward air (apâna); those on the right side are the mind-holders, the holders of the circulating air (vyâna); those on the left side are the ear-holders, the holders of the outward air (udâna); and those in the middle are the speech-holders, the holders of the pervading air (samâna).